Trouble installing Acrobat 9

i have new mac air after old 1 bit dust. trying "normal." browser chrome. osx el capitan 10.11.1

i have downloaded acrobat pro 9 per adobe directions.

i have obtained serial number.

i seem have successful download...and have "dragged" acro 9 folder applications folder.

i try open acrobat 9...no installer comes up, rather error message:

"can't opened because unidentified developer....only downloads mac app store , identified developers can installed."

i have believe adobe identified developer ...if can point me fix, appreciated.

thanks, mike

mac unidentified developer issue
--------------------------------

here's how open apps apple should not blocking:

More discussions in Downloading, Installing, Setting Up

adobe

Keep